Yes, agreed - I do plan to try this next - just discovered this http://www.kickstarter.com/projects/peterseid/romo-the-smart... (not self driving :-( ) robot which communicates via the phone's audio jack which would work well in this project. Additionally, this code could easily be used to control a Romo, so I'll probably try to order one of those too - would make the set up much more reproducible for others if the 'car' is ready made.